VDC Takes on Vac

IN THE PAST, CONTROL DEVICES have required coo much power to make 24 Vdc products cost effective or practical. During the past few years, industrial-control product manufacturers have placed more emphasis on 24 Vdc as the control voltage of choice. Design innovations, like increased microprocessor content and separation of control and power circuits, have reduced control-power requirements. The result has been dc power supplies with improved reliability at reduced costs. Technology advances in power-transistor ampere ratings have helped reduce the issues of excessive dc voltage drop over long cable runs. This has led to an increase in the variety of 24-Vdc-controlled devices along with improvements in quality, robustness, features, and size.